linux-kernel - [PATCH AUTOSEL 6.5 27/31] powerpc/85xx: Fix math emulation exception

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Message-Id: <20231018141151.1334501-27-sashal@kernel.org>
Date:   Wed, 18 Oct 2023 10:11:44 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>, npiggin@...il.com,
        sv@...ux.ibm.com, masahiroy@...nel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH AUTOSEL 6.5 27/31] powerpc/85xx: Fix math emulation exception

From: Christophe Leroy <christophe.leroy@...roup.eu>

[ Upstream commit 8e8a12ecbc86700b5e1a3596ce2b3c43dafad336 ]

Booting mpc85xx_defconfig kernel on QEMU leads to:

Bad trap at PC: fe9bab0, SR: 2d000, vector=800
awk[82]: unhandled trap (5) at 0 nip fe9bab0 lr fe9e01c code 5 in libc-2.27.so[fe5a000+17a000]
awk[82]: code: 3aa00000 3a800010 4bffe03c 9421fff0 7ca62b78 38a00000 93c10008 83c10008
awk[82]: code: 38210010 4bffdec8 9421ffc0 7c0802a6 <fc00048e> d8010008 4815190d 93810030
Trace/breakpoint trap
WARNING: no useful console

This is because allthough CONFIG_MATH_EMULATION is selected,
Exception 800 calls unknown_exception().

Call emulation_assist_interrupt() instead.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://msgid.link/066caa6d9480365da9b8ed83692d7101e10ac5f8.1695657339.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/kernel/head_85xx.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/head_85xx.S b/arch/powerpc/kernel/head_85xx.S
index fdbee1093e2ba..f9634111e82ed 100644
--- a/arch/powerpc/kernel/head_85xx.S
+++ b/arch/powerpc/kernel/head_85xx.S
@@ -396,7 +396,7 @@ interrupt_base:
 #ifdef CONFIG_PPC_FPU
 	FP_UNAVAILABLE_EXCEPTION
 #else
-	EXCEPTION(0x0800, FP_UNAVAIL, FloatingPointUnavailable, unknown_exception)
+	EXCEPTION(0x0800, FP_UNAVAIL, FloatingPointUnavailable, emulation_assist_interrupt)
 #endif
 
 	/* System Call Interrupt */
-- 
2.40.1